An investigation of navigational decisions

Strange, J. L. (1984) An investigation of navigational decisions. Doctoral thesis, City of London Polytechnic.


This work is concerned with an examination of how the Merchant Navy Navigators use the information provided by the different aids.

It is divided into three main parts. First are a series of experiments where seafarers studying for their Master’s certificate were presented with cards containing information from a number of different navigational aids, and asked to plot the position lines on a chart and then decide where they would consider the ships' position to be.

The second part was the design and construction of a simple non-interactive simulator based on slide displays and video recordings. The aids used were visual bearings, radar, Decca and the echo sounder. The information was taken from instrument readings recorded on board the training ship "Sir John Cass" during a voyage along the East coast from Southwold to Harwich. A number of flashing lights were included in the design to simulate the keeping of a lookout.

In the third part a similar group of subjects were asked to navigate a ship on two simulated voyages of half an hour's duration each, while at the same time to log the number of lights they observed. As a measure of their navigational ability they were asked to prepare a course to steer and an E.T.A. for a point about half an hour's steaming ahead of the position at the end of each exercise. A total of 17 dependent variables were identified during the experiment and these were tested in pairs for correlation.

From the results of these experiments it was possible to produce an order of the subjects' preference for the different aids, to demonstrate that the subjects preferred to use only two position lines when fixing their position and to examine how the subjects used these aids.

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